Issue #3073067 by phjou, hydrian: Deprecated function: strpos(): Non-string...

Issue #3073067 by phjou, hydrian: Deprecated function: strpos(): Non-string needles will be interpreted as strings in the future. Use an explicit chr() call to preserve the current behavior in private_message_preprocess_container()

private_message.module

@@ -595,7 +595,7 @@ function private_message_preprocess_field__private_message_thread__private_messa
  * depended upon.
  */
 function private_message_preprocess_container(&$vars) {
-  if (isset($vars['element']['#id'])) {
+  if (!empty($vars['element']['#id'])) {
     if (strpos('edit-members-wrapper', $vars['element']['#id']) === 0) {
       // Add a custom class to the private message members widget container.
       $vars['attributes']['class'][] = 'private_message_members_widget_default_wrapper';